Science Experiments - Variables

Science Experiments - Variables

CG KHOA

​

With

Teacher Toby

How scientists design an experiment

​Review

Multiple Choice

What is the scientific method?

• Doing experiments and seeing what happens

• A process we can use to find answers to questions

• How you become a scientist

• Reading from a science book

​Step 1: Observation

​​Step 2: Question

​​Step 3: Hypothesis

​​Step 4: Experiment

​​Step 5: Analysis & Conclusion

​​Step 6: Share Results

​

Today we will be looking at a very important part of the scientific method.

​The experiment.

Multiple Choice

What is the purpose of an experiment?

• To make things explode

• To mix chemicals together

• To test a hypothesis

• To guess what will happen

​Example from last week:

​Observation: The plant is dying.

​

​Question: Why is it dying?

​

​Hypothesis: I think it has not had enough water.

​

​Experiment: I will add water and see if the plant improves after 2 days.

Multiple Choice

Is this experiment perfect?

• Yes

• No

​New example:

​Observation: I have a new plant. Plants can die.

​

​Question: how can I help this plant be healthy?

​

​​Hypothesis?

What do we know about plants?

​

​

​

Multiple Choice

What could affect the health of a plant?

• The temperature

• The amount of sunlight

• The quality of the soil

• All of these things

​Hypothesis?

​What could make a plant more healthy?​

​The amount of water.

​​The amount of sunlight.

​​The quality of the soil.

​​The temperature.

​​etc...

​The Independent Variable

​​The independent variable is

something that you can change

in an experiment.

​​E.g. Amount of water given to a plant.

​​Or.. sunlight, temperature etc.

​

​The independent variable helps us to create our hypothesis.

​E.g I think that the right amount of water will help my plant stay healthy.

Multiple Choice

We change the independent variable in our experiment to help us to create a hypothesis and see how it affects our results.

• True

• False

How do we test our hypothesis?

​What makes a plant healthy?

​

​Growing tall.

​​Green colour.

​​Many leaves.

​​Fruit or flowers.

​​Etc.

The dependent variable​?

​The dependent variable is what can change BECAUSE of the independent variable.

​

​E.g How many leaves a plant has?

​​or... how tall is it? how many flowers?

​

​The dependent variable helps us to test out hypothesis.

​E.g. If the plant has more leaves if is healthy

Multiple Choice

The dependent variable is what we want to measure to test if our hypothesis is correct or not.

• True

• False

​How do I know my if my hypothesis is correct?

​Independent variable:

​The amount of water the plant gets.

​Dependent variable:

​How many leaves it has.

​

​How will I know how my independent variable is affecting my dependent variable?

Multiple Choice

How can I know if the amount of water is affecting the health of my plant?

• I could compare the plant to another plant to see which is healthier.

• I could see if the plant is healthier after the experiment.

• I could measure how much water I give the plant.

• I coul eat the plant and see how it tastes.

​If we have more than 1 plant, we can compare the independent & dependent variable.

​

​

​

​

​

E.g Different amounts of water + Different number of leaves

​My experiment

​​I have 3 plants.

​​1. My new plant in my bedroom.

​2. A plant in my living room.

​3. A plant in my garden.

​

They will all receive a different

amount of water for 1 month.

​​1. Will be watered every day. 2. Will be watered every 3 days

​& 3. will be watered every week.

Multiple Choice

What could be a problem if I use these plants in my experiment?

• I don't know the names of the plants.

• All the plants are different.

• I don't know how much water to give them.

• My dog pees on the plant that is in my garden.

Problem: These plants are all different!

​

​

The type of plant is different.

​The soil is different.

​The pot is different.

​The location is different.

​The Controlled Variables

​The controlled variables are all

of the parts of the experiment

that you keep the same.

​​E.g. The same: plant, soil, pot,

temperature, sunlight.

​

​The controlled variables help us to

​know how ONLY our independent variables will affect the experiment.

​e.g. how the water affects the plant, but not the other things.

Multiple Choice

I should change the controlled variables during the experiment to change the result.

• True

• False

​My improved experiment.

​​I have 3 identical plants:  ​1, 2 & 3. ​​They will all: 

​Have the same size pot, the same soil.

​Be in the same location.

​​They will all receive a different

amount of water for 1 month.

​I will check the health of each plant by ​counting the leaves.

​1. Will be watered every day. 2. Will be watered every 3 days

​and 3. will be watered every week.

​My improved experiment.

​

​I will give each plant a different

​amount of water.

​This is the Independent Variable.

​​I want to test the to see which plant

​grows more leaves.

​This is the Dependent Variable.

​​I will keep the plant, the soil, the pot

​and the location the same.

​This is the Controlled Variable.

Poll

Which plant do you think will be the most healthy?

• Plant 1:

  Water every day

• Plant 2: 

  Water every 3 days

• Plant 3:

  Water every week

​Analysis & Conclusion

​After 1 month I counted the leaves of each plant.

​

​Plant 1: 4 leaves (all brown)

​​Plant 2: 10 leaves (light green)

​​Plant 3: 17 leaves (dark green)

Multiple Choice

​Plant 1: 4 leaves (all brown)

​​Plant 2: 10 leaves (light green)

​Plant 3: 17 leaves (dark green)

What is our conclusion?

• All the plants are healthy

• Plant 1 is dead

• This type of plant is most healthy when is it watered every week.

• This type of plant needs a lot of water.

​​I will give each plant a different

​amount of water.

​This is the Independent Variable.

​​​I want to test the to see which plant

​grows more leaves.

​This is the Dependent Variable.

​​​I will keep the plant, the soil, the pot

​and the location the same.

​This is the Controlled Variable.