Question

A hypothesis is a possible explanation of an observation that can be tested by an experiment.

Plan a fair test to find out whether the colour of a cloth affects how quickly it dries in the sun. Write (a) your hypothesis, (b) the variable you change, the variable you measure and two variables you keep the same, and (c) how you will record your results.

A group measured the time for one spoon of sugar to dissolve in 100 mL of water at different temperatures (without stirring): 20 °C: 120 s; 40 °C: 75 s; 60 °C: 45 s; 80 °C: 30 s (a) Describe the pattern in the data. (b) What conclusion can be drawn? (c) Predict a likely range for the time at 50 °C and explain your prediction.

Meera noticed that bread kept in the refrigerator stays fresh longer than bread kept on the kitchen shelf. She suggested that mould grows more slowly at low temperature. To test this, she put six slices of the same bread in separate sealed plastic bags. She kept three bags on the kitchen shelf and three in the refrigerator, and checked them every day. The table shows the number of days until mould first appeared.