GRADE 7 PRELIMS

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A person puts warm water in an aquarium, thinking that fish would be more comfortable in it. However, the fish died. What could be the reason behind this?

• The concentration of oxygen decreases in warm water.

  
  
  

• 1. The concentration of oxygen increases in warm water.

• 1. The high temperature of water increases the fish's oxygen intake.

• 
  
  

  All of these

  
  

You decide to marinate chicken in an acidic mixture (like lemon juice or vinegar). What effect does the acid have on the meat?

• •  It cooks the meat immediately.

• • It helps break down proteins, making the meat more tender.

• It helps build proteins, making the meat firmer.

  
  

• • It adds color to the meat.

Jackson and Mia want to do an experiment to determine how the temperature of water affects how much salt can be dissolved in it.

In what order should they perform the following steps?

Step 1: With a teacher's help, bring the water in one of the beakers to the boiling point.

Step 2: Pour equal amounts of water into two identical beakers.

Step 3: Record how many half-teaspoons of salt are completely dissolved in each beaker.

Step 4: Gradually put salt into the water of each beaker, a half-teaspoon at a time.

• 1. 4 2 1 3

• 1. 2 1 4 3

• 1. 2 4 1 3

• 1. 1 2 4 3

In order to take off, an airplane has to generate enough lift (upward force due to air pushing on the plane) to overcome its weight (downward force due to gravity). The faster an airplane goes, the more lift it generates.

When discussing lift in a paper airplane, which principle is being referenced?

• The plane's weight

• Air pressure differences created by wing shape

• The force of gravity

• The speed of the throw

You are cooking a stew in a pressure cooker and another in a regular pot at the same temperature. After 30 minutes, you find that the stew in the pressure cooker is done while the one in the regular pot is still simmering. Which principle explains why the pressure cooker cooks food faster?

• Increased temperature reduces pressure.

• Increased pressure raises the boiling point of water.

• Decreased surface area increases cooking speed.

• Higher temperatures decrease cooking time.

After several rides, you notice that the roller coaster seems to be slowing down. What could be a real-world reason for this change in speed over time?

• The energy is being lost to friction and air resistance.

  
  

• The coaster's design is too efficient.

• Riders are becoming heavier over time.

• The coaster is gaining energy from the environment.

A botanist is doing an experiment to see how different light conditions affect the growth of pea plants. She plants the same number of seeds in three identical pots with the same type and amount of soil. One pot is kept in a dark closet, another is placed on a windowsill, and the third is put under a lamp with a green bulb. She waters all the plants the same amount every three days and measures how tall each plant grows every day for three months.

What is the main thing that the botanist is changing in this experiment?

• 1. The amount of soil in the pots

• 1. The light conditions for the plants

• 1. The amount of water given to the plants

• 1. The length of time the experiment runs