HMH Unit 2.3 Pgs 139-142

HMH Unit 2.3

Pgs 139-142

Electroplating

• Did you know electricity is able to cause a physical change? Engineers use electricity to cause physical changes that will protect objects from other physical and chemical changes happening.

• This process is called electroplating.

Electroplating

• Electricity is used to attach metal particles to other metals.

• The charge is used to join the particles of both metals together.

• In turn, this forms a material that is better protected. In this case neither the plated or plating metal changes, and the process is reversible.

Electroplating

• Once, pennies were solid copper.

• Today, pennies are made by using electroplating to cover small zinc plates with a layer of copper.

• Brass, like the process of pennies above, lets us get the original metal back.

Changes at Home: Cooking Science

• Did you know that there are all kinds of chemical changes that happen in the kitchen? Remember that a chemical change results in something new being produced and the original materials are used up, or changed into something else. 

  What types of things happen in the kitchen that result in new things being made?

Changes at Home: Cooking Science

• What types of things happen in the kitchen that result in new things being made? Do you like bananas? Bananas change from green to yellow as they ripen. Eventually, they turn brown and get mushy. Ripening is a chemical change.

Composting

• What do you do with any leftover food from a meal? Do you throw it away or do you put it into a compost pile? Composting is another example of a chemical change. The food scraps that go into it break down over time.

Making S'mores

• What do you get when you take graham crackers, chocolate, and marshmallows and add a chemical change? S’mores! While the different pieces of the s’more can still be seen, it is much harder to take them apart after heating.

Making Stir-Fry

• Making vegetable stir-fry on the stovetop is another example of a chemical change. As they cook, the vegetables get brown marks on them. These marks happen because of the heat of the stovetop.

  
  

  
  

Baking Bread

• Baking bread in the oven is a great example of a chemical change. What gets put into the dough for bread? Flour, sugar, yeast, and eggs are usually blended together. After the bread is baked, can these things come apart again?

  
  

  
  

Open Ended

What kinds of energy are causing chemical changes to occur when one is making food? Answer in complete sentences

Multiple Choice

Baking bread is an example of a _________ change.

• physical

• chemical

Multiple Choice

The ingredients of the bread _____ to form a new substance.

• mix

• separate

Multiple Choice

Once the bread is baked, the original ingredients can _____ be separated.

• always

• never

Open Ended

Describe a food that would include a physical and a chemical change in it. to make. Answer in complete sentences